1. Field of the Invention
Preferred embodiments of the present invention generally relate to an image forming apparatus for effectively cleaning a charging roller, and more particularly, to a cleaning roller shifting unit provided in the image forming apparatus that causes a cleaning roller to contact the charging roller for a predetermined time during a non-operation of image formation at predetermined intervals.
2. Discussion of the Related Art
In an image forming apparatus that employs an electrophotographic method to form an image, a photoconductor uniformly charged by a charging member in advance is irradiated with reflected light from a document such that an electrostatic latent image is formed thereon. Then, toner supplied from a developing device is applied to the electrostatic latent image such that a toner image is formed on the photoconductor. The toner image is transferred and fixed onto a sheet of transfer paper to form an image.
In such an image forming apparatus, since the charging member is disposed in contact with or in close proximity to the photoconductor, foreign material such as residual toner or paper particles remaining on the photoconductor are prone to attach to a peripheral surface of the charging member. Such foreign material attached to a peripheral surface of a charging member prevents the charging member from uniformly charging the photoconductor and results in image quality deterioration. Therefore, a variety of techniques have been proposed to remove foreign material attached to a charging member.
For example, a known technique has been proposed for removing foreign material attached to a peripheral surface of a charging roller by employing a cleaning roller that collects the foreign material on the peripheral surface and a separation mechanism that causes the cleaning roller to separate from the charging roller.
However, such a technique has a drawback in that frequent cleaning may shorten a life of a cleaning roller even though the technique sufficiently cleans a charging member and satisfactorily maintains performance of the charging member for a certain term. According to the technique, the cleaning roller cleans the charging roller at every image formation even though the charging roller does not require cleaning. The frequent cleaning may also cause waste and unfavorably affect the charging roller.